NEW YORK – Doc Rivers’s phone rang sometime around 6 a.m. yesterday, a concerned Boston Celtics owner calling to check on his coach and team.

The Celtics were already safely in New York, but forgive Steve Pagliuca for forgetting. This is a sad, confusing and chaotic time in Boston, and nobody is thinking about basketball first.

But the Celtics have a game to play today, the opener of their playoff series against the Knicks, and if they can provide a boost to their struggling city with some postseason success, that gives them even more motivation in their rare role as an underdog.

“I think when you go through tragedy as a city you kind of look for something to cling on, and really I believe that the city of Boston lives and dies with our sports teams and they’re going to be watching closely,” longtime Celtics star Paul Pierce said. “And you know there’s just a sense of pride about the city and a sense of pride about this team to go out there and kind of play well and to do the best we can for the city in the wake of the tragedy.”

The Celtics’ final home game of the regular season was to be Tuesday night, but that was canceled after three people were killed in the Boston Marathon bombings. They played at Toronto on Wednesday night and then came to New York, watching news reports yesterday that showed their city being virtually shut down while authorities hunted for one of the suspects.

Many people might switch away from the news coverage today looking for a diversion, and the Celtics know their performance might make a difference to some of them.

“I know it doesn’t hurt. I don’t know it if helps or not,” Rivers said. “Listen, for some people a basketball game’s not going to matter. Some people, just the joy of the sport and, you know, the victory and that, will help people. It’ll help people heal.”

The Knicks know all about playing for a hurting city. They opened their season days after SuperStorm Sandy devastated the New York area, and their emotionally charged 104-84 rout of Miami at Madison Square Garden jump-started them on the way to their first Atlantic Division title since 1993-94.

“I don’t even know how to put it into words, but you just wish those families nothing but the best,” Knicks Coach Mike Woodson said. “But you know Boston has always been a sports town, so they’ll rally around it and try to figure it out as they move up the road.”

The Celtics swept the Knicks in a first-round series two years ago. This time, New York is the No. 2 seed after ending Boston’s five-year reign as division champion and won three of the four meetings in the regular season.

Rivers downplayed the regular-season results, noting the Celtics dominated Atlanta during the 2007-08 season, only to be forced to seven games in the first round. But the Knicks clearly have gained confidence as they try to win a postseason series for the first time since 2000.

“It’s not going to be an easy series, we know that, but at the same time it’s a series that we’re going to win,” point guard Raymond Felton said. “We’ve got home-court advantage, so we’ve got to take advantage of it.”

With NBA scoring champion Carmelo Anthony and top sixth-man candidate J.R. Smith, the Knicks have been able to crack Boston’s once-stout defense. But a couple of those Knicks victories came when Kevin Garnett rested, so they expect to see a better Boston team.

But even if forced to play without starting guard Pablo Prigioni, who sprained his ankle in the regular-season finale, the Knicks believe they’re stronger than their teams Boston had been beating up on for years, especially knowing they get to start at Madison Square Garden.

“That was our goal, to lock down home court, and we did that, and now we have the opportunity to do something special, protect our home court,” Anthony said. “It won’t be easy, but we’re up for that challenge. We’re willing to take that challenge and it starts (today).”

The Boston-New York rivalry is one of the fiercest in sports, and the teams had their heated moment in the first meeting this season, when Anthony was suspended a game by the NBA for following Garnett to the Celtics’ team bus to confront him after they exchanged words during the game.

Pierce loves to hit big shots in New York and taunt the crowd after. The Celtics don’t expect anything to change today, no matter how much support their city is getting.

“You know, I played here. I know how crazy, the mindset of a New Yorker,” said Rivers, a former Knicks player who heard ‘Hey Doc, we love Boston’ at the team hotel.

“But I know what they mean,” he said. “They mean the city. They ain’t meaning the Celtics.”

Garnett expects only one type of reception at Madison Square Garden, no matter what’s happening back home.

“Terrible,” he said. “We’re on the road, period. Playoff time, on the road, Boston-New York.”

The Knicks will also host Game 2 on Tuesday night before the Celtics get to play in front of the home fans next Friday night.